javascript - 数组中内置Symbol.asyncIterator

Question

根据 MDN Web 文档:

There are currently no built-in JavaScript objects that have the [Symbol.asyncIterator] key set by default.

我的问题是这是如何起作用的:

function promises() {
    return [
        new Promise(x => setTimeout(() => x(1), 1000)),
        new Promise(x => setTimeout(() => x(2), 2000)),
        new Promise(x => setTimeout(() => x(3), 3000)),
    ]
}

for await (x of promises()) console.log(x) 

Answer 1

MDN 还指出

The for await...of statement creates a loop iterating over async iterable objects as well as on sync iterables, including: built-in String, Array, Array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined async/sync iterables - MDN (emphasis mine)